1. Field of the Invention
The present invention relates to a power supply apparatus with a power-saving function for use in .an information processing system.
2. Description of the Related Art
When a user utilizes an information processing system, it is troublesome for the user to turn on the power and start the system for every use thereof since a long waiting time is required so that the working efficiency is decreased. Accordingly, in general, the power to the system is always turned on even if it is not being used by the user, i.e., waiting (idle) time. From the view of power-saving, it is necessary to reduce the power consumption in the waiting time.
Recently, an international standard for power consumption (NUTEK; Spec 803299/92-92) has been established in the field of information processing system. This standard, established in Sweden, has been used as an international standard for the regulation of power consumption around the world.
According to this standard, briefly, the following specifications must be satisfied for a system to be considered to have a power-saving function. First, the power consumption in a stand-by or idle state of the system must not exceed thirty watts, and preferably, is under fifteen watts. Second, when the system is not used for more than seventy minutes, the power supply must automatically be turned off. However, if the power consumption of the system is under eight watts as a maximum value, preferably, under five watts, it is not necessary to turn off the power even if the system is not used more than seventy minutes.
Accordingly, it is desired to design a system to have a power consumption of eight watts, preferably, under five watts, in the waiting state.
In general, three states are considered for the power consumption, i.e., first, the power consumption at a normal use of the system; second, the power consumption at an initial detection of a start signal, a memory backup and heater back-up in a CRT; and third, the power consumption at the initial detection and the memory backup.
Therefore, it is desired to reduce the power consumption, particularly, the power consumption at the above second and third states under eight watts, preferably, under five watts, in the waiting state.